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A two-color Particle Image Velocimetry (PIV) technique has been applied to a motored single cylinder two-stroke motored research engine. In two-color PIV, two light sheets of different wavelengths are used to successively record, at a known time separation, the positions of the particulate seeds in the flowfield. By separately interrogating the two images of different color and cross-correlating them, a two-dimensional velocity field is obtained. Since the sequence of the images is known, directional ambiguity is eliminated and two-color PIV can be used to study complex, recirculating flows such as those found in an internal combustion engine. The technique is used here to measure the flow in the cup of a motored, single cylinder, cup-in-head, research engine operating with high swirl. Velocity fields were measured at several planes parallel to the piston crown. Multiple images were obtained at each plane, and ensemble averaged velocity and velocity fluctuation were determined.

The exciplex fluorescence technique has been used to separately visualize liquid and vapor phase fuel in engines since its development by Melton. However, as a fluorescence technique it has the potential to be quantitative and the underlying assumptions have been outlined by Melton. An initial quantitative application of the TMPD/naphthalene system, based on these assumptions, applied to a hollow-cone spray in a two-stroke engine, indicated that it substantially over-estimates the concentration of fuel vapor about TDC. The reasons for the discrepancy were investigated and it was concluded that a major factor is the effect of temperature on the photophysics of the species involved. Thus the absorption spectra of the exciplex dopants were determined at temperatures up to 700 K. These experiments showed that the increase in absorption with temperature above 500 K is responsible for the failure of the earlier calibration.

A two-color Particle Image Velocimetry (PIV) technique has been applied to a single cylinder, cup-in-head two-stroke research engine. In the two-color PIV, two wavelengths are used to successively record, at a known time separation, the positions of the particulate seeds in the flowfield. By separately interrogating the two images of different color and cross-correlating them, a two-dimensional velocity field is obtained. Since the sequence of the images is known, directional ambiguity is eliminated and two-color PIV can be used to study complex flows. The technique is here applied for the first time to an engine in the presence of combustion. The presence of combustion light complicates the application of two-color PIV because narrow band-pass laser line filters can not be used to reject it, however a suitable combination of laser power, colored glass filters and thresholding during interrogation allowed sufficiently high quality images to be obtained.